Imagine a set of face down cards that on the other side are either red or white.

You only know the number of cards and you'd like to know how many are red. But it costs alot to turn over cards and you're willing to accept some uncertainty. Try playing with the tool below to see if it might help.

X-axis is a parameter, k

Y-axis is probability that the true number of red cards in the population, K, is less than or equal to k